6BME:
reference: Lysine as a heme iron ligand: A property common to three truncated hemoglobins from Chlamydomonas reinhardtii., Johnson EA, Russo MM, Nye DB, Schlessman JL, Lecomte JTJ, Biochim Biophys Acta Gen Subj. 2018 Dec;1862(12):2660-2673. doi:, 10.1016/j.bbagen.2018.08.009. Epub 2018 Aug 10. PMID: 30251657

This OCA Structure page
uses Jmol, developed by the Jmol Development Team (documentation).